Living organisms are continuously subjected to various stresses from outer environment. To resist such stresses, they maintain their homeostasis by various regulatory systems. Among stresses, representative is an oxidative stress caused when a living organism fails to sufficiently cope with active oxygen produced by its endogenous and exogenous causes. Against this stress, living organisms have a system called redox regulation to cope with the stress to maintain their homeostasis by regulating the redox state. This system functions to adapt to many extrinsic factors, i.e., agents, radiation, ultraviolet ray, environmental pollutants, high fever, low temperature, hypoxic condition, and infectious diseases as well as to oxidative stress from lifestyle-related diseases such as cancer, diabetes, arteriosclerosis, hypertension and obesity. However, if this regulation mechanism is broken for some reasons or become unable to provide sufficient adaptation, oxidative stress occurs. Currently, some molecular markers enabling easy examination of whether or not the intracellular redox regulation is functioning and enabling early detection of occurrence are proposed.
For example, proposed is a method for detecting oxidative stress on a living organism comprising specifically measuring oxidized apolipoprotein AI present in a sample by sandwich method using two antibodies as antibodies, one of which is an antibody specifically reacts with an oxidized site of oxidized apolipoprotein AI and the other is an antibody against apolipoprotein AI, wherein the method is available for mechanism analysis and clinical diagnosis of oxidative stress-related diseases such as arteriosclerosis and diabetes complications, e.g., nephropathy and neuropathy (for example, see Patent Document 1). Also proposed is a method utilizing, for example, a diagnostic plot of an oxidative stress profile, which is a two-dimensional coordinate system with its ordinate representing oxidative damage index calculated from oxidative damage items which shows a magnitude of oxidative damage caused by active oxygen and free radicals occurred in a living organism (generation rate of 8-hydroxy 2′-deoxyguanosine in urine per body weight, generation rate of 8-epi-prostaglandin F2α in urine per body weight, oxidation ratio of coenzyme Q10 in serum, and lipid peroxide content in serum) and with its abscissa representing a protective capacity against oxidation calculated from anti-oxidation items which shows antioxidant capacity to suppress and prevent oxidation of constituents of a living organism caused by active oxygen and free radicals occurred in a living organism, wherein values of a test subject can be filled in the plot (e.g., see Patent Document 2-4). Also proposed is a monoclonal antibody that recognizes a substance correlated with oxidative stress in a living organism and that specifically recognizes dihydropyridine structure (e.g., see Patent Document 5). However, since little is established about an indicator that can be measured from blood or urine, it was difficult to provide a living organism with prevention against oxidative stress.
On the other hand, a method for comprehensively measuring intracellular metabolites by a measuring method of metabolites in a sample with a capillary electrophoresis-mass spectrometer (CE-MS) (e.g., see Non-Patent Document 1) is a method to qualitatively and/or quantitatively determine low molecular weight compounds (metabolites) pattern and/or peptides pattern in a liquid sample from a human or animal body in order to monitor the human or animal body conditions. In this method, the metabolites and peptides in the liquid sample are separated by capillary electrophoresis, then directly ionized, and detected by an online-interfaced mass spectrometer. To monitor the human or animal body conditions for a long time, sample values and reference values representing said conditions, and the deviation obtained from such values and the correspondence between them are automatically stored in a database. For separation and analysis of anionic compounds using a combination of capillary electrophoresis and mass spectroscopy, known is a method for separation and analysis of anionic compounds wherein electro-osmotic flow is reversed by a coated capillary which has a cationic ion pre-coating in its inner surface (e.g., see Patent Document 7).    [Patent Document 1] Japanese Laid-Open Patent Application No. 2004-69672    [Patent Document 2] Japanese Laid-Open Patent Application No. 2003-310621    [Patent Document 3] Japanese Laid-Open Patent Application No. 2003-302396    [Patent Document 4] Published Japanese translation of PCT international publication No. 2002-517724    [Patent Document 5] Japanese Laid-Open Patent Application No. 11-80198    [Patent Document 6] Published Japanese translation of PCT international publication No. 2003-532115    [Patent Document 7] Japanese Patent Publication No. 3341765    [Non-Patent Document 1] Soga, T., Ohashi, Y., Ueno, Y., Naraoka, H., Tomita, M., and Nishioka, T., “Quantitative Metabolome Analysis Using Capillary Electrophoresis Mass Spectrometry”, J. Proteome Res. 2. 488-494, 2003.